Turbine engines are now well known, and the turbine engine is now known to have several advantages not to be found in engines such as, for example, piston type internal combustion engines, although such engines have useful features not heretofore incorporated in turbine engines.
As is well known, the typical turbine engine utilizes compression and combustion stages with fluid flow established therethrough, utilizes near constant high pressure at combustion (practical usable pressures, at least in many turbine engines, are limited by reverse flow through the compressor (i.e., compressed stall) and the physical size of the several stages required to achieve the necessary high pressures), and has a primary direction of flow through the engine that is substantially parallel to the axis of rotation (circumferential components may be found in radial compressors, but these components do not provide progress of the fluid between successive stages of the engine).
It is known that the efficiency of heat engines is directly related to the operating temperatures at which heat is added, that increases in operating pressures normally also increase operating temperatures, and that heat engines can be made more efficient by constraining the fluid during the heating process, all of which enhance efficiency, and the foregoing have been found to be applicable to heat engines in which heat is added by combustion of, or in, the working fluid. While constraining of working fluid to a near constant volume during heating is common to the internal combustion engine, for example, this feature has not heretofore been utilized in now known turbine engines.
Now known turbine engines normally cannot tolerate pressure rises during combustion because of accompanying temperature rises to unacceptable levels and/or because pressure rises above the pressure at the outlet of the compressor results in pressure flow back through the compressor with such pressure back flow often stalling the compressor.
While compressor/inlet stall has been prevented in a pulse jet engine, for example, by interposing a barrier between the combustion chamber and the compressor/inlet during the combustion process to allow the temperature and pressure to rise during combustion above that provided by the compressor and thus provide an increase in operating efficiency, and while this same general concept has also been used in a piston driven internal combustion engine through use of inlet and outlet valves with the piston operated in such a manner as to provide a near fixed volume during combustion to thus provide an increase in operating efficiency, the foregoing has not heretofore been utilized in now known turbine engines.
In turbine engines, the maximum operating temperatures typically occur at the exit from the combustor, which commonly is also the inlet of the turbine portion of the engine, and the materials, or surfaces, at the turbine portion are often continuously subjected to temperatures at, or near, the maximum tolerable operating temperatures.
Since the maximum tolerable temperature strength of the materials in the turbine portion of now known turbine engines is at least one of the primary determinants of turbine efficiency, such engines are thus also now limited in efficiency by the ability of the materials in the turbine portion to withstand high temperatures (while increased efficiency in now known turbine engines could be realized by improving the high temperature strength of the material at the turbine portion, this cannot always be practically accomplished and/or is often quite an expensive undertaking).
Improvements in a turbine engine to provide efficiency enhancement not now found in the turbine engine would therefore be found useful and/or is now needed.